Abstract
BackgroundPreimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) is widely applied in couples with single reciprocal translocation to increase the chance for a healthy live birth. However, limited knowledge is known on the data of PGT-SR when both parents have a reciprocal translocation. Here, we for the first time present a rare instance of PGT-SR for a non-consanguineous couple in which both parents carried an independent balanced reciprocal translocation and show how relevant genetic counseling data can be generated.MethodsThe precise translocation breakpoints were identified by whole genome low-coverage sequencing (WGLCS) and Sanger sequencing. Next-generation sequencing (NGS) combining with breakpoint-specific polymerase chain reaction (PCR) was used to define 24-chromosome and the carrier status of the euploid embryos.ResultsSurprisingly, 2 out of 3 day-5 blastocysts were found to be balanced for maternal reciprocal translocation while being normal for paternal translocation and thus transferable. The transferable embryo rate was significantly higher than that which would be expected theoretically. Transfer of one balanced embryo resulted in the birth of a healthy boy.Conclusion(s)Our data of PGT-SR together with a systematic review of the literature should help in providing couples carrying two different reciprocal translocations undergoing PGT-SR with more appropriate genetic counseling.
Highlights
Preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) is widely applied in couples with single reciprocal translocation to increase the chance for a healthy live birth
Are double translocations associated with double risks? Here, we for the first time present a healthy live birth derived from a non-consanguineous couple carrying two different reciprocal translocations involving four chromosomes by PGT-SR combine with translocation breakpoint identification and show how relevant genetic counseling data can be generated
The probability of normal/balanced zygotes for such couples was estimated to be 16.6% (40.7% × 40.7%) without considering nontranslocation chromosomes abnormalities. Another large practical PGT-SR data of the European Society of Human Reproduction and Embryology (ESHRE) PGT Consortium showed that 19.5% (4681/23960) day-3 embryos were transferable after genetic testing when one of the partners is a carrier for a reciprocal translocation [8], and this rate increased to 30.0% (142/473) when biopsy at the blastocyst stage [12]
Summary
Preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) is widely applied in couples with single reciprocal translocation to increase the chance for a healthy live birth. Limited knowledge is known on the data of PGT-SR when both parents have a reciprocal translocation. We for the first time present a rare instance of PGT-SR for a non-consanguineous couple in which both parents carried an independent balanced reciprocal translocation and show how relevant genetic counseling data can be generated. For reciprocal translocations, unbalanced gametes are likely to be generated owing to abnormal segregation patterns at meiosis. We for the first time present a healthy live birth derived from a non-consanguineous couple carrying two different reciprocal translocations involving four chromosomes by PGT-SR combine with translocation breakpoint identification and show how relevant genetic counseling data can be generated. We reviewed the available literature to estimate the reproductive risk and discuss counseling approaches when couples with double reciprocal translocations
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